Medical procedures involving the vertebrae are normally complicated because of the preciseness and accuracy required to avoid both neural damage and injury to major blood vessels. Precision depth guided instruments are required to perform percutaneous spinal surgery. These surgeries sometimes require penetration of the hard cortical bone of the vertebra and traversal of the softer cancellous bone lying thereunder. A large force is normally required by the surgeon to penetrate the cortical bone. Once the cortical bone is penetrated, extreme care must then be taken to avoid rapidly penetrating through all of the cancellous bone. There is also the danger of rapidly passing through the cancellous bone and then through the cortical bone on the other side of the vertebra. This can result in injury or damage to the spinal cord and/or other organs or blood vessels located adjacent the spine. In some instances, the force required to penetrate the cortical bone is greater than a surgeon can apply by hand. In these instances a hammer or other similar instrument is required to force the instrument through the cortical bone. When a hammer or similar instrument is used, there is a greater danger of the instrument passing rapidly through the cancellous bone and out the other side of the vertebra. Preexisting conditions such as osteoporosis may complicate this problem.